This invention relates generally to an energy storage system, and more particularly to a method and apparatus for determining the health of a battery block that may be utilized in a locomotive.
Railroad locomotives typically include a diesel engine that is coupled to a traction drive system that provides the propulsion force for the locomotive. To start the diesel engine, locomotives include an energy storage system that is utilized to start the diesel engine and to provide electrical power to various devices installed on the locomotive. During operation, an alternator driven by the diesel engine, continuously recharges the energy storage system to ensure that the energy storage system remains charged to a predetermined voltage level.
To facilitate maintaining the operational readiness of the locomotive, the energy storage system is monitored to evaluate the effectiveness of the charging system and to ensure that the energy storage system is maintaining a proper charge. More specifically, at least one known locomotive implements the energy storage system utilizing a plurality of battery blocks. To monitor the health of the battery blocks, the battery blocks are periodically tested by measuring the specific gravity in each battery using a hydrometer, for example. However, utilizing the hydrometer to determine whether the battery is “good” or “bad” is not always effective. For example, data illustrates that at least some battery blocks have been removed from locomotives after failing the hydrometer test. Under more strenuous testing conducted at an off-site facility, it was determined that a smaller percentage of the battery blocks removed were defective. However, a larger percentage of the battery blocks removed were shown to be acceptable or “good” battery blocks. As a result, significant time and costs have been expended by the railroads removing, transporting, and testing battery blocks that were eventually determined to be operating correctly. In general there are two batteries in a locomotive containing 16-cells each. Each 16-cell battery is referred to as one monoblock. There are a total of 32 of cells in a set of locomotive batteries. The open circuit voltage of a fully charged cell is approximately 2.1 Volts. Two batteries connected in series provide approximately 67 Volts for the complete battery. It is common practice in rail road industry to check and service these batteries every 90-days. The practice has been to check the specific gravity of acid using a device called hydrometer. The test is time consuming as specific gravity of acid in each cell is measured. Opening the cap, drawing acid from the cell, and recording the specific gravity takes 3-4 minutes costing about 90-120 minutes every ninety days. Moreover, the hydrometer provides in-correct readings due to varying state-of-charge (SOC) of batteries as locomotive arrives in shops with different level of battery energy.